Sverdlov was born in Nizhny Novgorod as Yakov Mikhailovich Sverdlov to Jewish parents Mikhail Izrailevich Sverdlov and Elizaveta Solomonova. His father was a politically active engraver who eventually went into forgery, and arms storage and dealing partially to support his family. The Sverdlov family had six children: two daughters (Sophia and Sara) and four sons (Zinovy, Yakov, Veniamin, and Lev). After his wife's death in 1900, Mikhail converted his family to the Russian Orthodox Church, married Maria Aleksandrovna Kormiltsev, and had two more sons, Herman and Alexander. Yakov's eldest brother Zinovy was adopted by Maxim Gorky, who was a frequent guest at the house. Yakov Sverdlov joined the Russian Social Democratic Labour Party in 1902, and then the Bolshevik faction, supporting Vladimir Lenin. He was involved in the 1905 revolution.

After four years of high school, he became a prominent underground activist and speaker in Nizhny Novgorod. For most of the time from his arrest in June 1906 until 1917 he was either imprisoned or exiled. During the period 1914–1916 he was in internal exile in Turukhansk, Siberia, along with Joseph Stalin.

A close ally of Lenin, Sverdlov played an important role in the controversial decisions to close down the Constituent Assembly and to sign the Treaty of Brest-Litovsk. It was claimed that Lenin provided the theories and Sverdlov made sure they worked. Later their relationship suffered as Lenin appeared to be too theoretical for practical Sverdlov.

A number of sources claim that Sverdlov played a leading role in the execution of Tsar Nicholas II and his family.

A book written in 1990 by the Moscow playwright Edvard Radzinsky claims that Sverdlov ordered their execution on 16 July 1918. This book as well as other Radzinsky's books were characterized as "folk history" (Russian term for pseudohistory) by journalists and academic historians.[1][2][3][4][5] However Yuri Slezkine in his book The Jewish Century expressed the same opinion: "Early in the Civil War, in June 1918, Lenin ordered the killing of Nicholas II and his family. Among the men entrusted with carrying out the orders were Sverdlov, Filipp Goloshchekin (ru) and Yakov Yurovsky".[6]

The 1922 book by a White Army general, Mikhail Diterikhs, The Murder of the Tsar’s Family and members of the House of Romanov in the Urals, sought to portray the murder of the royal family as a Jewish plot against Russia. It referred to Sverdlov by his Jewish nickname "Yankel" and to Goloshchekin as "Isaac". This book in turn was based on an account by one Nikolai Sokolov, special investigator for the Omsk regional court, whom Diterikhs assigned with the task of investigating the disappearance of the Romanovs while serving as regional governor under the White regime during the Russian Civil War.[7]